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1 ///////////////////////////////////////////////////////////////////////////////
2 //
3 /// \file       crc64.c
4 /// \brief      CRC64 calculation
5 ///
6 /// Calculate the CRC64 using the slice-by-four algorithm. This is the same
7 /// idea that is used in crc32_fast.c, but for CRC64 we use only four tables
8 /// instead of eight to avoid increasing CPU cache usage.
9 //
10 //  Author:     Lasse Collin
11 //
12 //  This file has been put into the public domain.
13 //  You can do whatever you want with this file.
14 //
15 ///////////////////////////////////////////////////////////////////////////////
16
17 #include "check.h"
18 #include "crc_macros.h"
19
20
21 #ifdef WORDS_BIGENDIAN
22 #       define A1(x) ((x) >> 56)
23 #else
24 #       define A1 A
25 #endif
26
27
28 // See the comments in crc32_fast.c. They aren't duplicated here.
29 extern LZMA_API(uint64_t)
30 lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc)
31 {
32         crc = ~crc;
33
34 #ifdef WORDS_BIGENDIAN
35         crc = bswap64(crc);
36 #endif
37
38         if (size > 4) {
39                 while ((uintptr_t)(buf) & 3) {
40                         crc = lzma_crc64_table[0][*buf++ ^ A1(crc)] ^ S8(crc);
41                         --size;
42                 }
43
44                 const uint8_t *const limit = buf + (size & ~(size_t)(3));
45                 size &= (size_t)(3);
46
47                 while (buf < limit) {
48 #ifdef WORDS_BIGENDIAN
49                         const uint32_t tmp = (crc >> 32)
50                                         ^ *(const uint32_t *)(buf);
51 #else
52                         const uint32_t tmp = crc ^ *(const uint32_t *)(buf);
53 #endif
54                         buf += 4;
55
56                         crc = lzma_crc64_table[3][A(tmp)]
57                             ^ lzma_crc64_table[2][B(tmp)]
58                             ^ S32(crc)
59                             ^ lzma_crc64_table[1][C(tmp)]
60                             ^ lzma_crc64_table[0][D(tmp)];
61                 }
62         }
63
64         while (size-- != 0)
65                 crc = lzma_crc64_table[0][*buf++ ^ A1(crc)] ^ S8(crc);
66
67 #ifdef WORDS_BIGENDIAN
68         crc = bswap64(crc);
69 #endif
70
71         return ~crc;
72 }